<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      function fun() {
        function fun1() {
          let num = 8
          function fun2() {
            function fun3(num) {
              console.log(num) // 打印多少为什么
            }
            fun3(num)
            num = 5
          }
          num = 3
          fun2()
          console.log(num) // 打印多少为什么
        }
        let num = 1
        fun1()
      }
      fun()


      //  3 和 5
    </script>
  </body>
</html>
